QLC vs TLC

QLC (quad-level cell) and TLC (triple-level cell) are NAND flash cell types. TLC stores three bits per cell and QLC stores four. TLC has to tell eight charge states apart, QLC sixteen, so the states sit closer together and reads and writes need more precision and checks. Four bits instead of three is one third more data per cell. Solidigm puts the cost in performance.

Solidigm's D5-P5336 is 192-layer QLC in U.2, E3.S and E1.L, from 7.68 to 122.88 TB. It is rated 0.42 to 0.60 DWPD over 5 years, 134.3 PBW at 122.88 TB, and power-off retention of 3 months at 40 degrees C. Solidigm's D7-PS1010 is 176-layer TLC rated 1.0 DWPD, 28 PBW at 15.36 TB. At 15.36 TB the QLC drive is rated 14.7 PBW. Solidigm estimates the 122.88 TB D5-P5336 can take nonstop 32 KB random writes for five years and keep about 5 percent of its life.

Pick QLC for read-heavy tiers where capacity per slot or per watt is the limit. Pick TLC when sustained writes approach the QLC rating of 0.42 to 0.60 DWPD or the job is write-heavy. Measure the daily write volume first.

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Last verified October 30, 2026.